Chapter 5 Results

5.1 New York City’s Arrests

In the result section, you will find visualizations, and the insights derived from the cleaned & preprocessed NYC Arrest dataset, organized around the concepts of 3 Ws: What, Where, and When.

5.1.1 What:

5.1.1.1 What is the distribution of Arrest Types?

First of all, let’s use a bar plot to visualize the general distribution of arrest category. Since there are a lot of arrest types, I would only show the top 15 counts of the arrest types. In this way, we are able to visualize what kind of crimes are happening and being arrested in NYC.

From the plot, we can observe that the highest number of arrests made by NYPD is to the type of “Dangerous Drugs”, having 466735 cases, significantly higher than the counts of rest of types. Indeed, NYC always has a bad reputation with dangerous drugs. The second highest count is the type of “Assault 3 & Related OFFENSES”, which suggests the relative safety problem faced by NYC residents every day. We need to have tighter laws and control towards drugs as this is the most serious and frequent arrest categories.

Next, let’s investigate the distribution of arrests count throughout NYC’s 5 boroughs.

5.1.1.2 What is the distribution of arrest rate in each NYC boroughs?

In the above bar plot, we calculated the average arrest rate of NYC residents across the ten year interval, from 2012-2021. The plot, suggests that for each year, residents in Manhattan will be arrested for an average of 0.046 times, the highest rate across the five boroughs. Bronx is the second highest with a rate of 0.045. Both rates are significantly higher than the rate of the rest of 3 boroughs.

Netx, let’s check the

5.1.1.3 What kind of crimes do different age groups tend to commit?


First of all, for residents whose age are older than 65, they barely commit any crimes or being arrested by NYPD. As expected, the arrests made by NYPD are heavily concentrated on the age group of 25-44. The second highest age group is 18-24. It indicates that most crimes committed and offenders arrested are in a relatively young age. For the distribution of offenders’ age group younger than 65 vs arrest categories, we find that for age group from 18-64, “dangerous drugs” has the highest number of arrests made, which is consistent with the overall arrest categories distribution. For teenager who is under 18, however, “robbery”, “assault” and “dangerous drugs” all have similar numbers of arrests, with robbery being the slightly highest. Unlike for other age groups, robbery stands out to be the most frequent one. This is alarming. We need to build better programs and have better education to get more teenagers off the streets and back to school.

For the distribution of offenders’ race vs arrest categories, first we found that there are barely any arrests made to “American Indian / Alaskan Native”, presumably because of the low populations of the group living in New York City. For the rest of the races, we can observe that, except for “Asian / Pacific Islander”, all the offenders in the other races were being arrested due to “dangerous drugs” most frequently. For “Asian / Pacific Islander” residents, the highest arrest category is “Assault 3 & Related Offenses”. Additionally, there is an alarming trend: The number of arrests made to black NYC residents is significantly higher than that of any other races. Is there a systematic discrimination against black people in the arrests made by NYPD? In the When section, we will use time series data to find out. However, better education and benefits program are necessary to solve this situation.

For the distribution of offenders’ sex vs arrest categories, intuitively the number of male offenders are significantly higher than the number of female offenders. Interetsingily, for female offenders, the highest arrests made are to the category of “Assault 3 & Related Offenses”, with “Petit Larceny” and “Dangerous Drugs” being closer for the second and third. On the other hand, male offenders in NYC are usually arrested for “Dangerous Drugs”, which is consistent with the overall distribution.

In the next section, let’s use some maps to explore and visualize the locations as well as each arrests being made.

5.1.2 Where:

We will use New Yorkc City’s map to visualize the type and location of the arrests occurred. For normal citizens, they are more concerned about crimes of theft, assault, weapons as well as robbery. Thus, we will create a map to visualize the frequencies of occurrences of these types of arrests.

For crimes regarding theft, from the map, we can observe that they are heavily concentrated in Manhattan’s mid town and downtown. Most New York City’s business centers and financial centers are located there, which explains the high case counts of theft. After all, mid town and downtown locate NYC’s central business district.

From the map of weapon related arrests, we can observe that they are mostly concentrated in Harlem of Manhattan, Bronx and Brooklyn. These three neighborhoods also have heavy gang activities, which corresponds to the heavy weapon related crimes. Regular residents should avoid traveling through these locations alone, especially on foot, as the regions are flooded with guns.

For the map of assaults & murder related arrests, we can observe that they are mostly made in the population-heavy areas. However, Upper Manhattan and Bronx have the worst problem of assault & murders, which is consistent with the map of weapon related arrests.

For the map of robbery related arrests, similarly, cases are heavily concentrated in Harlem, Bronx. Also, downtown and mid town Manhattan have high cases counts as well. Due to the higher concentration of middle class and upper class people in mid town and downtown Manhattan, it has become a location of robbery as well.

5.1.2.1 Columbia University

As Columbia Lions, we are also curious about the arrests being made around the campus, especially for Where are the most frequent places and how should we avoid the areas? Let’s find out in the following maps.

From the two maps, we can observe that the further from the campus, the more arrests are being made. For instance, as we get closer to Harlem, arrests of Assault, Murder and Robbery are increasing. Therefore, we would want to stay close to the campus, when we travel alone.

5.1.3 When:

In this section, we would like to investigate the development of the trend of arrests categories throughout 2012-2021. How is the overall arrests distribution developed over time? How has the types of arrests being made changed over time? We will use ridge plots and line plots to find out.

Due to the high number of the arrest categories, we will first focus on the top 15 arrest categories. The ridge plot indicates that, for each type of the top 15 Arrest types, the overall distribution is moving toward a downward trend. The number of arrests made to the major arrest categories are all decreasing toward the end of 2021. For instance, there is a sharp decrease since 2018 for “Dangerous Drugs” and a sharp decline for “Petit Larceny” since 2016. It could suggests that the overall safety in NYC is getting better. Less and less offenders are being arrested by NYPD throughout 2012-2021.

Similarly, let’s see how the trend of crimes in each boroughs change throughout the years, using a line plot.

The above plot also shows that for each of the borough, the crime counts are decreasing from 2012-2021. Even though in 2014 and 2016 there are a little spikes in crime counts, the overall trends are in decline, especially for recent years. This finding also corresponds to our previous findings that the overall arrest counts in NYC is in a downward trend. additionally, we can observe that, except for Staten Island, the gaps of arrests counts between the other four boroughs are closing and the arrests count of the four boroughs are all converging toward a lower number at the end of 2021.

5.1.3.1 Arrests Trend for Teenage Perpetrator

As mentioned in the previous section, the distribution of arrests made to teenagers are different to the other age groups. Here, we would want to visualize the trend of teenage crimes, how has the crime categories changed throughout the years?

As we can observe from the ridge plot, the overall trend is promising as the number of arrests made to teen offenders is declining. A lot of teenagers were arrested for the possession of stolen property from 2012 - 2014, and the number suddenly drops. Also, for the highest counts arrest categories of teenagers, “Dangerous Drugs”, “Robbery” and “Assault 3 & Related Offense”, they are all decreasing from 2012-201. However, we can observe that there are some increasing trends in certain arrest categories. For instance, ’Murder & Non-NEGL. Manslaughter”, “Unauthorized use of a Vehicle” and “Criminal Mischief & Related OF” are all spiking in 2020 and 2021. Even though the overall number of crimes committed by teenagers are decreasing, we should be alert of the increase in certain categories.

Next, we will use a summary table to describe the effect of Covid pandemic to the arrests made in New York City.

5.1.3.2 What’s the effect of Covid to the general arrest / crime trend in NYC? Let’s use a table to indicate the summarized difference

Table 5.1: Arrests Categories that experienced Decrease after Covid
Arrest_Category Arrest_Count_Before_Covid Arrest_Count_After_Covid Percentage_Change
OFFENSES INVOLVING FRAUD 1070 2051 91.682%
BURGLARY 4647 5997 29.051%
MURDER & NON-NEGL. MANSLAUGHTE 1040 1207 16.058%
DANGEROUS WEAPONS 7070 7158 1.245%
Table 5.1: Arrests Categories that experienced Decrease after Covid
Arrest_Category Arrest_Count_Before_Covid Arrest_Count_After_Covid Percentage_Change
DISORDERLY CONDUCT 644 33 -94.876%
OTHER STATE LAWS 795 78 -90.189%
FRAUDULENT ACCOSTING 123 15 -87.805%
ADMINISTRATIVE CODE 576 72 -87.500%
THEFT OF SERVICES 448 78 -82.589%
OTHER OFFENSES RELATED TO THEF 3321 590 -82.234%
VEHICLE AND TRAFFIC LAWS 11917 3642 -69.439%
FRAUDS 794 291 -63.350%
OTHER TRAFFIC INFRACTION 2626 1033 -60.663%
PROSTITUTION & RELATED OFFENSES 898 357 -60.245%
THEFT-FRAUD 318 128 -59.748%
OTHER STATE LAWS (NON PENAL LA 1037 437 -57.859%
INTOXICATED & IMPAIRED DRIVING 4280 1961 -54.182%
PETIT LARCENY 20422 10088 -50.602%
CRIMINAL TRESPASS 2784 1391 -50.036%
GAMBLING 578 292 -49.481%
FORGERY 4058 2108 -48.053%
DANGEROUS DRUGS 19011 10744 -43.485%
OFFENSES AGAINST PUBLIC ADMINI 7543 4432 -41.244%
ALCOHOLIC BEVERAGE CONTROL LAW 524 315 -39.885%
INTOXICATED/IMPAIRED DRIVING 561 338 -39.750%
GRAND LARCENY 9626 5805 -39.695%
NYS LAWS-UNCLASSIFIED FELONY 1014 619 -38.955%
RAPE 812 546 -32.759%
SEX CRIMES 3965 2764 -30.290%
OFFENSES AGAINST THE PERSON 991 706 -28.759%
BURGLAR’S TOOLS 697 498 -28.551%
ASSAULT 3 & RELATED OFFENSES 31205 23191 -25.682%
ROBBERY 9713 7284 -25.008%
ARSON 139 106 -23.741%
MISCELLANEOUS PENAL LAW 11761 9038 -23.153%
POSSESSION OF STOLEN PROPERTY 2233 1739 -22.123%
UNAUTHORIZED USE OF A VEHICLE 627 501 -20.096%
CRIMINAL MISCHIEF & RELATED OF 9646 7756 -19.594%
OFF. AGNST PUB ORD SENSBLTY & 3854 3137 -18.604%
FELONY ASSAULT 15446 13372 -13.427%
GRAND LARCENY OF MOTOR VEHICLE 1220 1200 -1.639%

We compared the arrests made for the two time intervals, one pre Covid between 2019-04-01 to 2020-04-01 and the other post Covid between 2020-04-01 and 2021-04-01. As expected from the previous explorations, there is a decrease in the arrests made to the most types of crimes post Covid. This is likely due to the government’s relief packages as well as the lockdown measures. However, there are four crime types that experienced increase since the Covid pandemic. For “Offense Involving Fraud”, the number of arrests made increases from 1070 to 2015, a total increase of 92%. After Covid, people may prefer conduct businesses through online platforms, which gives offenders more opportunities to commit fraud. The arrests count of “Burglary”, and “Murder & Non-Negl Manslaughter” also increases significantly, 29% and 16% respectively. Covid pandemic is taking a tow to many people, and for some, they sought to extreme measures toward their problems.